GEOSCIENCE AND MINES BRANCH
An Examination of Coastal Erosion and
its Impact on the Port Hood Station
Provincial Park and Beach, Inverness
County, Nova Scotia
P. W. Finck
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Halifax, Nova Scotia
May 2015
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An Examination of Coastal Erosion and its
Impact on the Port Hood Station Provincial Park
and Beach, Inverness County, Nova Scotia
P. W. Finck
Introduction
Port Hood Station Provincial Park is located immediately south of Port Hood, Inverness County (Fig. 1).
Taylor (2004) and Taylor and Soehl (2005) identified several coastal processes that they presumed were
having a negative impact on the park. These included erosion of the foreshore, erosion of the seaward
side of the foredune, sea-level rise, and limiting of sediment supply to the northwest-facing part of the
beach at the park. Recently, two issues have been identified that are of concern to members of the local
area and business community. The first is shoreface erosion that is undermining parts of the boardwalk
and observation platform. The second is long-term migration of the fronting dune system that is
progressively burying the boardwalk behind the dunes.
The provincial Parks and Recreation Division of the Nova Scotia Department of Natural Resources
(NSDNR) brought the situation to the attention of staff in the NSDNR Geological Services Division and
requested that they undertake an assessment of erosion and infrastructure sustainability at the park. This
is the third study conducted in this area within the last decade. The first study was carried out by Robert
(Bob) Taylor of the Geological Survey of Canada (Atlantic) in 2004. The report was not formally
published by the Geological Survey of Canada, but was distributed locally in Nova Scotia. Bob Taylor
was responding to a request from Jim MacLean, County Councillor, for advice on a 2003 proposal to
Figure 1. Air photo of Port Hood Station Park and Beach. Numbered locations correspond to figure numbers.
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armour the shoreline. The second study was undertaken by Brian Taylor and Virginia Soehl of Jacques
Whitford in 2005. This report was prepared for the Parks and Recreation Division of NSDNR. They
again examined erosion and described various options that could be taken to reduce erosion at the park.
Both of these studies are extremely helpful as they describe in detail the shoreline and dune system as it
existed ten years ago and also contain an excellent photographic record. It will become apparent in this
report how dramatically coastal processes have changed over the last decade at the park. This study will
enhance the knowledge and expertise of staff of the Geological Services Division since such
scientifically robust, site-specific historical detail is not usually available when examining coastal
processes in Nova Scotia.
The author visited the site in late July 2014. The park was visited twice over two days. It was noted that
the parking lot was near capacity and that the beach and walkways were busy. The park and beach were
toured with members of the Port Hood Area Development Society in order to gain an understanding of
issues that are important to the local community. It is the author’s understanding that the society raises
money to construct infrastructure at the park and to undertake general maintenance (grass cutting,
installing sewage/bath facilities, boardwalk maintenance, etc.). The concerns of the community appeared
to be threefold: (1) the cost and difficulty of raising sufficient funds by the community for maintenance
and operation of what is a provincially owned park, 2) erosion and wave action that is undercutting and
causing failure of a section of the boardwalk, and 3) migration of the dunes that are burying a significant
section of the boardwalk. This report will address problems of erosion, infrastructure failure and dune
migration, and will suggest ways to make infrastructure more sustainable, thus reducing operating costs
of the park. It is outside the mandate of the Geological Services Division to discuss matters related to
park funding.
Coastal erosion and sea-level rise are natural coastal processes that have been happening in Nova Scotia
for thousands of years. Even without ongoing net sea-level rise, coastal erosion in many areas in Nova
Scotia will continue for thousands of years. This is because Nova Scotia’s coast has been out of
equilibrium with fluctuating sea levels since the last deglaciation, which commenced approximately
18,500 years ago.
Since the last deglaciation, rates of coastal erosion have varied due to changes in factors such as land
subsidence, extent of sea ice, varying intensity and frequency of cyclonic events (e.g. hurricanes and
named post-tropical storms), and cyclic changes in the amount and intensity of rainfall. These are just a
few of many variables. In Nova Scotia, direct measurements of the rate of coastal erosion are typically
restricted to small study areas. Comprehensive measurements and analysis of erosion rates around the
province are not available. However, around the province, erosion rates are known to vary from a few
centimetres a year (or less) to as much as 1.5 m a year based on decadal averages. Based on the author’s
experience, a rate of 30 cm a year, or approximately 1 ft. a year, is a reasonable average estimate of the
rate of coastal erosion if the province is considered in its entirety; however, the actual rates are highly
site-and geographic region specific.
Coastal erosion due to sea-level rise has been an issue for centuries in Nova Scotia. However, because
larger amounts of increasingly costly infrastructure have been built close to the coast in recent years, this
issue has become more complex and also more widely recognized.
Previous Work
The reports by R. Taylor (2004) and B. Taylor (2005) are very similar in their descriptions of the
sedimentary environment at Port Hood Station Provincial Park. Both reports are extensive, detailed and
invaluable to the present study.
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Taylor (2004) described the foredune at the back of the southwest-facing beach (Fig. 1) as “a single
ridge, well vegetated along the crest and back slope with only vegetation along its upper seaward
slope.” The lack of vegetation on the lower seaward side of the foredune is important as it often
indicates an unstable, erosive sedimentary environment. This is particularly true if there is significant
undercutting of the top of the dune, which causes vegetation and sand to collapse onto the area at the
immediate base of the foredune. Care must be taken with this interpretation, however, because Taylor
(2004) visited the site on April 23rd when winter storms have often buried or destroyed the tops of
vegetation. In my experience, parts of a beach that appear devoid of vegetation in April through early
June may be covered by thick vegetation by mid-August. However, Taylor (2005) visited the site on
September 23, 2005, when vegetation would have had ample time to re-establish, and observed the
same lack of vegetation as Taylor (2004). The observation by Taylor (2005) suggests that the lack of
vegetation is erosional rather than seasonal. He described the area as follows and the description is
very similar to that of Taylor (2004). “The seaward face of the dune is somewhat vegetated with signs
of wave erosion. Blowouts have occurred in several areas, probably initiated by foot traffic accessing
the beach .... Some vegetation exists on the upper part of the beach below the dune.” That description
was for the area immediately south of Dean Shoal (Fig. 1), but the entire western facing beach south of
Dean Shoal was similar.
Taylor (2004) used aerial photographs to describe and measure changes in the width of the foreland,
both along the southwest-facing and northwest-facing sides of the park. The foreland is roughly the
area extending from the front of the dunes to the low-tide mark. Changes in the width of the foreland
along the western side of the park were noted. The width of the foreland increased from 107 m to 158 m
between 1939 and 1953, while between 1953 and 2009 the width decreased to 105 m, basically back
to its original 1939 width of 107 m.
Taylor (2004) did not state if he had rectified the aerial photographs using computer software to
remove distortion in the images and if he then measured the width of the foreland on the resulting
computer generated image. Rather, he stated that “the dimensions of the foreland were measured by
ruler on each of the three air photographs.” This suggests that he did not rectify the images, which
questions the reliability of the measurements. Depending on what part of the photographs was
measured, distortion could result in dramatic errors in measured distances. The numbers also contain
significant error as the measured widths of the foreland (measured from the base of the foredune to the
edge of the water) were not corrected for the position of the tide (i.e. was the tide low, medium or
high). Taylor stated, “tidal corrections were not applied (measured from dune to seaward edge of
sediment visible).” On beaches with a low slope, such as the southwest-facing beach, the error in such
measurements could be up to fifty per cent.
The reports by Taylor (2004) and Taylor (2005) are also of great value to the author as they contain
detailed descriptions and imagery of the northwest-facing beach. Since one report was produced in the
spring and the other in the fall, they help to eliminate seasonal variation. Taylor’s (2004) report can be
summarized as describing an eroding upper foreshore and predominantly a cobble beach on the
northeastern portion of the northwest-facing beach (Fig.1). Farther southwest the beach is mainly sand
with limited vegetation at the top of the beach in front of the foredune. The front of the foredune has
very little vegetation and is eroding. This description is also an adequate summary of the findings in
the Taylor (2005) report. Both reports agree that erosion will continue along the northwest-facing
beach. Taylor (2004) did state, somewhat contradictorily, “There is a good chance that the north shore
could improve naturally [presumably meaning a reduction in the rate of erosion, possibly stabilization.—
Author], there is also a good chance it could deteriorate further....” Taylor (2005) was more emphatic
and suggested “that the beach [at the park] is likely to continue to erode, particularly in light of sea
level rising.” Taylor (2004) noted that an observed increase in vegetation in the backshore would
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increase sand trapping and encourage dune growth, but that this would “leave less sand available for
beach growth.” He also noted, again paradoxically, that a decrease in the width of the foreland would
decrease the amount of wind-blown sand. Both reports are less specific with respect to the long-term
evolution of the southwest-facing beach.
Taylor (2004) also calculated the width of the foreshore along the northwest-facing beach.
Measurements of the foreshore indicated that it had decreased in width from 129 m in 1939 to 79 m in
1953 and finally to 53 m in 1999. These numbers are subject to significant uncertainty as described
previously. Regardless of the potential error, given the magnitude and unidirectional nature of the
possible decrease in width, in the present author’s opinion it suggests that the foreshore may have
decreased in width. However, the magnitude of the reduction cannot be quantified based on the
methodology of Taylor (2004).
Both reports discussed mitigation options, but specifically for the northwest-facing beach near the
general area of the picnic park. These can be summarized as (1) armouring by construction of a
revetment, (2) constructing a seawall, (3) rebuilding the causeway between Port Hood and Port Hood
Island, (4) beach nourishment by adding sand and vegetation, and (5) acquire more land, do nothing and
retreat.
Present Observations and Interpretation
The Port Hood Station Park faces both northwest and southwest toward the Northumberland Strait and
Gulf of St. Lawrence. The park is sheltered from north, east and to a lesser extent south winds by Cape
Breton Island. It is also well sheltered from westerly winds by Port Hood Island. The northwest-facing
part of the park (beach) is exposed to north by west to northwest by north winds. The southwest-facing
side of the park and beach are exposed to west by south to south by west winds. Seaward of the
southwest-facing beach, the water is shallow and this greatly reduces the size of swells moving onto the
beach. A similar situation exists for the northwest-facing beach. Because of the shallow water depths,
shoreface erosion is primarily driven by wind-generated waves.
The erosive force of waves is reduced because the southwest and northwest beaches are wide, have a low
seaward slope, and offshore of the beaches the water depth is shallow. Waves approaching offshore and
striking this type of beach break offshore and rapidly lose energy—rather than breaking against the
upper beach, dunes or scarp—except under high-tide and major storm conditions. The beaches vary in
width and have a low slope angle. Because of this, the remaining waves running up the beach rapidly
losesenergy. Even at high tide, the water depth is such that the base of the waves drags on the beach and
rapidly lose energy before striking the upper beach face and dunes.
The site visit occurred in late July 2014. At this time of year, barring strong winds and high-surf
conditions, sand typically accumulates in the intertidal and supratidal parts of beaches in Nova Scotia.
During winter when wave energy is typically higher, sand is often transported seaward and stored, and
moves landward when conditions favour deposition rather than erosion. Thus, wave energy conditions as
described above are likely to change somewhat in the winter. The beach is likely to be steeper, more
gravel and cobbles are typically present, and waves penetrate farther up the beach into the supratidal
area. It is the seasonal balance of these two processes and net sand loss or gain in the system that
determines beach stability.
There were no bedrock outcrops observed by the author within the main area of the park along the coast.
The eastern end of the park in the area of the changing and bathroom building and septic disposal field is
composed of till (Fig. 1). The till in this area has a moderately cohesive matrix composed of clay, silt
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and sand. The matrix surrounds pebble-, coarse gravel-, cobble- and small boulder-sized rocks. Erosion
of the till appears to be a local source of much of the pebble- and cobble-sized rocks that are found as a
lag below the low-tide mark and along the top of the beach above the high-water mark. The eroded till
matrix serves as a source of sand for the beach and dune systems. Additional material is derived from
bedrock and till exposed along the coast south and north of the park.
Till is exposed locally along the supratidal area of the northwest-facing beach (Fig. 2A) near the main
parking lot (Fig. 1) and extends to the base of the erosion scarp. At this point it is overlain by 1–1.5 m of
sand (Fig. 2B). Till was not exposed, or at least not observed by the author, elsewhere in the park.
Westward along the northwest-facing beach, exposures of till disappear. The beach above high tide is
composed of sand. However, near the base of the beach scarp there is a well formed pebble- to cobblesize rock lag (Fig. 3). This lag is found along the base of the scarp to an area just west of the boardwalk
and observation platform (Fig 1), which now extends out over the beach. From the observation platform
west, the intertidal part of the beach is sand. Above high tide, the sand extends to the base of the frontal
dune system (Fig. 4). The upper beach in front of the dunes is well vegetated. The vegetation can be
observed to catch and trap wind-blown sand that is transported from the northwest (Fig. 4). There are no
obvious dune blowouts as described by Taylor (2004). Small sections of an old (pre-2004) and now
nearly buried snow fence (Fig. 5) can be observed along the beach west of the observation platform. The
author was advised by a member of the Port Hood Area Development Society that the snow fence was
erected and Christmas trees placed behind the fence in an attempt to reduce erosion. This is one of the
few areas the author has visited where a snow fence, placed to reduce erosion, hasn’t simply been
destroyed by waves, leaving scattered vertical posts that are visually unappealing and a safety hazard.
The snow fence, whether by design or coincidence, seems to have been effective in trapping sand.
However, areas along the northwest-facing beach, where no evidence of a snow fence was observed, are
also trapping sand. The area is characteristic of a stable and even prograding (growing seaward) beach
system (Fig. 6). The foredune is generally well vegetated and very high; though not directly measured, I
estimate that it is in the order of 5-6 m. This beach and dune morphology extends westward to a
northward-curved spit referred to as Dean Shoal by Taylor (2005; Fig. 1). There are some localized
places in the area approaching Dean Shoal where the front of the foredune is less well vegetated, though
there are no blowouts and no areas of undercutting, and it thus appears to be relatively stable (Fig. 7).
From Dean Shoal south along the beach and the southwest-facing side of the park, the beach is quite
wide, including the intertidal and supratidal zones. It is composed of sand and scattered pebble- to small
cobble-sized rocks. The beach is backed by a high, well vegetated and stable foredune (Fig. 8). Seaward
of the foredune is a wide area of well established vegetation that is actively trapping windblown sand,
Figure 2. (A) Eastern end of northwest-facing beach, looking east, and (B) eastern end of northwest-facing beach,
looking west.
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Figure 3. Undercutting and erosion on northwest-facing beach, just west of the observation platform.
Figure 4. Sand aggrading as it is being and trapped by vegetation in front of the foredune on the
northwest-facing beach.
which is transported generally from the south (Fig. 9). Landward of this foredune is a second ridge that
is interpreted as representing the position of an older, now abandoned foredune. This area is also typical
of a stable and prograding (growing seaward) beach system (Fig. 10). The foredune fronting the
northwest-facing beach has undergone extensive growth since the 2004 and 2005 studies. While building
upward, it has also migrated landward, partially covering the boardwalk. The landward side of the
foredune is in places now well beyond the boardwalk. The central part of the boardwalk would have
been covered by the dune except that the Port Hood Area Development Society has cleared the sand and
cut back the dune (Fig. 11). This is becoming increasingly difficult as the boardwalk is now sided on the
northwest by a high, in some areas vertical, artificial dune-face and on the southeast by as much as
one-half metre of dune.
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Figures 5A and 5B. Images show snow fence almost buried in the face of the foredune as it advances (prograding
seaward) along the top of the northwest-facing beach.
Figure 6. Image shows well vegetated, prograding seaward face of the foredune along the top of the northwestfacing beach.
Erosional and Depositional Environment—Present
Interpretation
It is clear that the overall shoreline and the coastal sedimentary environment at Port Hood Station
Provincial Park and Beach have changed dramatically since the field visits and reports by Bob Taylor
(2004) and Brian Taylor (2005). It is unfortunate that images from those reports cannot be reproduced in
this report so that they could be compared by readers to the 2014 imagery (Fig. 2-11).
It should be noted that the 2004 site visit occurred less than seven months after Hurricane Juan passed
over Nova Scotia on September 29, 2003. The 2005 site visit was approximately two years after
Hurricane Juan. The author is not familiar with the extent of damage that Hurricane Juan may have
caused to the Port Hood shoreline. It is possible that the damage observed in the two earlier studies
might have appeared worse than what is typical for the area. It is common for beaches to show varying
degrees of recovery after major storm-related erosion events.
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Figure 7. Minor erosion of the foredune located east of Dean Shoal (Fig. 1).
Figure 8. Well vegetated and highly stable back beach and foredune area south of Dean Shoal (Fig. 1).
The northwest-facing shore has undergone extensive foredune growth as noted previously. The issue of
possible future burial of the boardwalk wasn’t a concern in 2004 and 2005. At that time, the bay fronting
Port Hood Station Park was clearly visible to people walking along the central part of the boardwalk.
Erosion and wave wash-over was the prevailing concern. Progressive vertical growth and migration of
the foredune and associated burial of the boardwalk is now a major concern and will worsen over time.
The entire northwest-facing beach in 2004-2005 was considered to be in a long-term phase of erosion
and system collapse. However, the northeastern-most part of the beach is now vegetated and stable (Fig.
2A). From there southwest to just past the observation platform, the beach scarp still shows erosion but
it appears to be greatly reduced (Fig. 2B). A comparison of the relative positions of the three picnic
shelters in this shoreline environment shows significant changes from 2005 (Taylor, 2005, photo 1) to
observations made by the present author in 2014. At present, the shoreface is now farther seaward,
contains far fewer cobbles and flat rocks, has far less exposed till, and has far more sand and vegetation.
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Figure 9. Minor exposure of sand along a short section of the seaward-facing side of the foredune south of Dean
Shoal.
Figure 10. Image shows the abandoned foredune along the southwest-facing beach at the park.
This does not mean that the coastal environment has switched from one of erosion and retreat to
deposition and progradation. Rather it may be a result of inadvertent beach nourishment in this area,
which will be discussed in a later section of this report.
From this area west to Dean Shoal, the coastal environment has switched from erosion and retreat to
deposition and progradation, both within the foredune and the upper beach face. The upper beach face is
well vegetated, shows few signs of erosion, and is actively capturing windblown sand (Figs. 4 and 6).
The southwest-facing beach (described above) was previously described by Taylor (2005) as a foredune
with blowouts and as having a non-vegetated, eroding seaward face. The upper foreshore was also
characterized by Taylor (2005) as having sporadic vegetation. At the time of the present author’s visit,
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Figure 11. Landward side of the foredune progressively covering the boardwalk as the dune builds in height and
width and moves landward.
this had changed dramatically. From Dean Shoal south along the southwest-facing beach the foredune is
well vegetated and stable. There is a well developed and wide vegetated zone fronting the foredune
along the upper foreshore that is actively capturing windblown sand. If this process continues, it is
possible that a new foredune will begin to grow in front of the existing foredune, similar to that
described along the Oregon coast by Reckendorf (1998), though in that case new foredune growth was
initiated by planting of a non-local grass.
Previous Erosion Mitigation Efforts
The author was advised by members of the Port Hood Area Development Society that approximately
five years ago shoreface stabilization was attempted along the northwest-facing beach in the area of the
picnic park and parking lot. Sand-filled geotextile tubes (geotubes) were placed parallel to and in front
of the upper shoreface in front of the then existing erosion scarp. The author is familiar with the use of
these geotubes along parts of the New England and northeast United States coast. They are considered a
softer and less intrusive alternative to rock armour. Geotubes typically are put in place, filled with sand,
and then buried with existing beach or imported sediment with the intent that they protect the shoreface
and allow vegetation to become established, thus creating a natural-looking shoreline.
As far as the author is aware, the geotubes on the northwest-facing beach were installed as outlined
above. However, by the next spring the sediment used to bury the geotubes had washed-out from around
the structure. The geotubes were reburied, but by the following spring they had again been exposed.
However, this time the geotubes had been heavily damaged, compromising their structural integrity so
that they had to be removed.
Though the cause for failure at Port Hood Station Park is unknown to the author, it is suspected that
winter ice was probably a contributing or decisive factor. Sea ice being pushed on shore exerts
tremendous pressure on artificial structures. In addition, sea ice is sharp and if the geotubes were
exposed due to a loss of surrounding material, then it is probable that ice could have punctured or cut the
geotubes. Sharp rocks can also become embedded in sea ice, and such rocks can act as a tool that cuts
the geotube. In addition, erosion of the cover and surrounding sediment along with possible undercutting
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could have resulted in movement of the geotubes. Movement of the geotubes could also result or
contribute to their rupture.
This example serves as a cautionary note to other companies, individuals or government bodies that
might consider using such a system for coastal protection. A large portion of Nova Scotia’s coastline is
subject to very high energy levels, and many other areas are also subject to significant winter ice.
Sediment-filled geotubes and bags may not be a suitable method of coastal protection along much of
Nova Scotia’s coastline. Before using any coastal protection system, and in particular when undertaking
large and expensive projects, a properly trained geoscientist or a coastal engineer should be consulted.
As described in the previous section, the area fronting the picnic park on the northwest-facing beach
showed little erosion in 2014 relative to the position of the shoreline in 2004 and 2005. Placement of the
geotubes in this area presumably required the importation of a significant amount of sediment, both to
fill the tubes and to then cover them. Though the tubes failed, presumably the sediment remained, either
along the upper shoreface or offshore where it may have been subsequently transported on shore when
energy levels permitted. Thus, though the geotubes failed, the sediment used in their placement may
have resulted in an inadvertent program of beach nourishment that may have been partially successful.
Addressing Community Concerns
As indicated previously, community concerns that the author can address are (1) migration of the
foredune that is burying a significant section of the boardwalk and (2) erosion and wave action that is
undercutting and causing failure of a section of the boardwalk and observation platform.
In the author’s opinion there are no reasonable options available to address the problem of burial of the
boardwalk (Fig. 11). The local business development association is doing the only thing possible, which
is removal of the sand that accumulates on the boardwalk. They are utilizing snow fence and are even
building vertical wood walls to prevent migration of the foredune. These are stop-gap measures that will
over time become untenable. It is not realistic to build a new boardwalk elevated to a height such that it
is above the top of the landward expanding foredune. If having a boardwalk in the future is a priority for
the community, then it will need to be moved well landward of the foredune and rebuilt. The higher it is
rebuilt, and the farther it is built from the advancing dune, will determine its functional lifetime.
Estimating the functional lifetime would be based on determining the rate of landward and vertical
growth of the foredune. This has not been determined.
It is not recommend that the boardwalk be rebuilt higher up on the foredune and closer to the beach. It
would again be buried by sand, or if the seaward face of the foredune was to again erode and retreat,
then the boardwalk would be undercut. During the author’s discussion with members of the Port Hood
Area Development Society, they noted that a flat side-rail nailed directly on top of either side of the
boards on the walkway made removal and replacement of damaged or rotten boards very difficult. Any
future reconstruction should obviously avoid that construction method. With respect to construction of
elevated boardwalks, building codes should be examined to determine at what height side rails are
required to be placed as this would be a significant additional cost and/or liability in the event that rails
were not present.
With respect to the short section of boardwalk near the observation platform and the actual observation
platform, it is the author’s opinion that these structures are not sustainable (Fig. 12). In the spring of
2014, the platform had collapsed onto the beach. The local development society raised money for
repairs. Volunteers reconstructed the damaged sections, and the platform was lifted up and posted. This
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is a commendable effort on the part of the local residents and demonstrates their commitment to the
park. The following comments are not intended in any way by the author as a criticism of these efforts.
The most seaward part of the boardwalk leading to the eastern side of the observation platform is being
undercut by erosion. In order to prevent continued erosion, some sort of shoreline stabilization is
required. Without considering how and at what cost this might be achieved, the sustainability of the
platform needs to be considered. It does not appear that the platform was originally constructed with the
intent of being a raised, post-supported platform. The main structure was fastened with nails that will not
withstand wave impact or shifting of the platform (Fig. 13). Platforms and walkways built out over
beaches (if sustainable) at other provincial parks are commonly constructed out of much larger wood
beams and are heavily bolted. The bolt visible in Figure 13 apparently was installed in the spring of
2014. When the platform was posted in 2014, each post was fastened with a single bolt (Fig. 14). Posts
installed for this purpose must have at least two bolts and must also have heavy cross bracing. In
addition, where the single bolts were used, each bolt was driven through a drilled hole in the wood
without having the nuts tightened (Figs. 13 and 14). Thus, the posts attached to the underside of the
platform are nearly free-floating, allowing the platform to twist and move when impacted by waves or
sea ice. In addition, the author was advised that the posts are only set down into the beach approximately
60 cm. Posts used for this purpose should be set down into the beach a minimum of 2 m (preferably
more), and they need to be attached to a structural member (preferably concrete) so that the posts cannot
lift. In the author’s opinion the platform is structurally deficient and is not sustainable in its present
form.
Options for Coastal Stabilization
The Port Hood Area Development Society did not specifically request that the author address coastal
stabilization methods. However, stabilization of the northward-facing beach upper shoreface from the
picnic park west to the observation platform is a viable option, so some comments are given here.
Stabilization would reduce or prevent future erosion near the picnic park and allow the boardwalk and
observation platform to be sustainable in their present position.
Figure 12. An image of the present observation platform looking east-northeast.
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Figure 13. Structural deficiencies in the framing of the observation platform at the park.
Figure 14. Image shows structural deficiencies in the construction of the posts supporting the observation platform.
A wide variety of erosion prevention measures are commonly used in Nova Scotia and other
jurisdictions. It is beyond the scope or purpose of this report to present an overview of the various
stabilization methods. In addition, suitable options depend on many different factors, chiefly but not
exclusively the varying geological, ecological and energy levels that occur at different sites. There is
also consideration of potential impacts on adjoining properties of various mitigation options. The value
of the infrastructure that needs to be protected, the ability to move it economically, and the fiscal
resources available to undertake various mitigation options are also considerations. In addition, the
present site is susceptible to seasonal ice-thrusting. This precludes all stabilization methods that might be
applicable to low-energy environments.
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The Taylor (2004) and Taylor (2005) reports discussed mitigation options specifically for the northwestfacing beach near the general area of the picnic park. These can be summarized as follows: (1) construct
a seawall, (2) rebuild the causeway between Port Hood and Port Hood Island, (3) armour the upper
shoreface by constructing a revetment, (4) nourish the beach by adding sand and vegetation, and
(5) acquire more land, do nothing and retreat.
Seawalls
Seawalls are effective at preventing erosion behind the wall. However, waves impacting the seawall
create significant turbulence at the base and in front of the seawall. This turbulence often, but not
always, causes erosion and loss of sediment in front of the seawall. Even where there isn’t sediment loss,
what was once sand in front of the seawall often becomes a cobble beach, at least in the supratidal area
extending down to the intermediate tide level. The author rejects construction of a seawall at this
location as a viable option.
Causeway
There is little or no evidence that rebuilding the causeway between Port Hood and Port Hood Island
would have a significant effect on erosion or deposition at the park. Even if it were beneficial, there is
the reality of the high cost versus benefit and the fiscal reality facing municipal and the provincial
government in Nova Scotia. In the opinion of the author this is not a realistic option for consideration or
even further investigation.
Armouring
Construction of a revetment along the shoreface between the picnic park and the area just west of the
observation platform is a viable option worthy of detailed discussion. A revetment in the most simplistic
sense is a pile of large armour stone placed or dumped against and out from the base of a cliff. A
schematic of a typical engineered revetment is shown in Figure 15.
The section of shoreline between the picnic park and west of the observation platform has a low scarp. It
is easily accessible for both delivery and placement of the armour stone. Machinery can work across all
of the tidal cycle. Till is present and a key excavated into the till (i.e. a trench dug below the surface of
the beach in which the bottom of the revetment is constructed) would serve as a stable base for the
revetment. Armouring would allow the boardwalk near the observation platform to remain; however, the
platform would need to be removed to allow placement of stone. Once the stone was placed, a
sustainable observation platform could be rebuilt over the revetment. The revetment must be carefully
designed to effectively join the foredune to the west without causing erosion. The revetment would
absorb wave energy, and since it would be constructed in the supratidal part of the beach, scouring in
front of the revetment should be minimal. Given the somewhat sheltered nature of the northward-facing
beach, the low slope of the foreshore and the shallow offshore bathymetry, a minimalist approach to
construction of the revetment could be considered. However, the lower armour stone would have to be
large enough to resist sea-ice thrusting. A suitably trained coastal geologist or coastal engineer should be
consulted in undertaking this type of work.
The armour stone has to be of sufficient size that it is not moved by storm wave action. The void spaces
between the stones have to be small enough to prevent waves from penetrating through the stone,
impacting the cliff, and washing out the cliff material through the holes between the individual stones.
The armour stone must also reach a height sufficient to prevent wave-overtopping as this results in
washing out of the cliff face behind the armour stone. In Nova Scotia, such structures are often built by
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Figure 15. Illustration of a stable revetment that meets best-practice geotechnical design parameters.
simply dumping large amounts of armour stone in a haphazard or partially organized manner (placed by
machine) in front of, piled up against, and dumped down over the face of the cliff or slope that requires
stabilization. This is referred to by the author as the ‘dump and run’ method. Depending on the size,
competency and amount of stone used (among many other factors), such a method may or may not be
effective. This method does not generally meet best-practice geotechnical design criteria and is an older
and now less commonly used method of coastline stabilization in Nova Scotia. In the author’s opinion it
is often susceptible to long-term failure.
In more recent years, it appears that contractors have become more knowledgeable, and revetments are
built using a variety of suitably sized armour stone and rip-rap backfill. Depending on the geotechnical
characteristics of the cliff or slope that is being stabilized, the use of a geotextile may or may not be
required. The stonework is carefully placed to ensure maximum stability and resistance to ice effects and
wave impact. It is also designed to prevent the cliff face from slumping behind the revetment, thus
damaging the structural integrity of the revetment. Typically the revetments do not meet all of the
best-practice construction methods, but they are far superior to former dump and run methods of
construction. A revetment may last multiple decades (even generations) depending on the sophistication
of the design and construction, and given that long-term maintenance is undertaken.
The cost of armour stone purchased at a pit varies but may range from four dollars per tonne to around
eight dollars per tonne. However, the cost of transporting the stone from a pit to a work site is extremely
high; the vast majority of the final cost is for delivery to the site. The cost of a job can be greatly reduced
if the stone can be delivered near the work, for example within reach of the excavator that will perform
the placement of the stone or within reach of a second excavator that could move the stone to the
excavator that will place it. If the stone has to be dumped even a short distance from the construction site
and then has to be transported a second time to the actual construction site, then the cost of the
revetment will increase dramatically. In addition, and particularly relevant to coastal construction, if tide
cycles limit the time that machinery can work at the site or restricts delivery of stone to the work site,
then this will also dramatically increase the cost of a revetment.
If armour stone is mainly dumped without significant placing of individual stones and without using
more complicated designs, then the time required to complete the project is significantly reduced.
Specifically, the time required for an excavator with an opposable claw to place the stone is significantly
reduced. This has to be balanced with the cost of hauling more stone than is typically required for a
more engineered design. If the source of the armour stone is close to the project site, relatively speaking,
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this should be reflected in the cost of the project. Individuals pricing a project should be familiar with
these facts, and there should be significant cost differences in quotes received from a contractor with a
nearby source of stone versus a contractor who has to obtain the stone from a significantly more distant
source. Keep in mind that contractors often own their own quarries and may want to use stone from their
quarry, thus affecting delivered stone cost. However, property owners should be aware that a cheaper,
locally sourced stone in some areas may be geotechnically inferior to more expensive stone from a more
distant source Use of inferior stone types is a common source of failure in coastal protection systems in
some areas of Nova Scotia. The cheapest quote may not be the best.
When constructing a revetment, rip rap should be placed rather than dumped. A skilled operator using an
excavator equipped with an opposable claw can quickly pick up boulders of various sizes and place them
so as to minimize spaces between the rocks and to create a strong, interlocking structure. One must take
care to use large enough armour stone to resist ice thrusting and the effects of having ice freeze onto the
rocks and dislocate rocks as the ice moves laterally or vertically at the face of the revetment. These are
two reasons for placing the armour stone so as to eliminate as many spaces between the rocks as
possible. In addition, an individual boulder has many sides. If the ice can freeze fast to three sides (for
example), it will be able to exert far more translational force on the boulder than if it only has one face to
freeze fast to. If a slab of ice is stuck between two boulders, when it is moved by tides or currents it will
exert far more force on the boulder than a layer of ice only frozen on the outer face of the boulder.
A geotechnically designed revetment, particularly where high erosion scarps are involved, will in the
authors opinion typically use less stone, which should reduce the large cost component associated with
stone transport. In addition, it would prevent waves from penetrating through the armour and impacting
the sand and till behind the revetment, thus preventing washout behind the structure. However, the
geotechnical revetment will require more time to carefully place the stone. This should be partially offset
by the reduced amount of stone that needs to be moved to the project site. The cost of a large excavator
on site should be somewhere in the range of $1000 to $1150 a day. Note that the dollar figures given in
this report are approximate and are only given for reference and explanation purposes. Coastal
stabilization projects are typically quoted on a job basis and calculated based on the length of the
shoreline being stabilized with consideration also given to the height of the revetment. For reference, the
cost for armouring along the Northumberland Strait of Mainland Nova Scotia is typically in the range of
$200 to $300 a metre when stone can be delivered directly to the site.
Beach Nourishment
As previously discussed, beach nourishment appears to have already been at least partially effective at
reducing erosion near the picnic park, if the author’s interpretation of the failed geotubes is correct. In
the author’s opinion, this is an alternate though more risky option to construction of a revetment.
Consideration could be given to importing large quantities of sand that contain a proportion of pebbles
and/or cobbles. The sand would temporarily protect the scarp while it was reworked and redistributed by
wave action. The exposed cobbles would create a paving or armouring effect, hopefully preventing too
much loss of the imported sediment. If the eroded sediment remained stored just offshore of the beach,
then under low-energy conditions it would move back on shore. It needs to be stated that under this
option the sustainability of the existing observation platform is less likely than under the revetment option.
In a previous section, the author referred to the dump and run method of armouring, and not in a
favorable manner. Consideration could be given to a hybrid of the dump and run and beach nourishment
approaches. The placement of modestly sized stones on the face of dunes in Cape Breton has proven
effective in capturing wind-blown sand and, with subsequent growth of vegetation, has effectively
resulted in dune growth (Fig. 16). Placement of a row of large armour stone a very short distance
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seaward of the base of the beach scarp could be used to break waves and prevent sea-ice damage.
Placement of geotextile would hopefully prevent erosion of the scarp behind the row of armour. The
area between the armour and the geotextile could be nourished by filling it first with coarse stone and
sediment against the armour, then filling it back and up to the top of the scarp against the geotextile with
a graded mixture of rock and finer sediment. The overall structure should be built higher than the
existing scarp to allow for erosion and washout of material while the structure hopefully stabilizes. This
should be accompanied by a sustained effort of replanting vegetation. Plants and bushes such as wild
rose and maram grass have deep roots, are drought tolerant and can withstand wave action.
Acquire More Land, Retreat or Do Nothing
The author has not specifically examined the landward extent of the park, though it is noted that the
local community does not own the park; it is Crown land. Regardless, generally there appears to be
sufficient property to allow for erosion on a multi-decade or longer time frame. However, this is
problematic near the parking lot as long-term erosion, if it occurs, could impact boardwalks and the
parking lot itself.
The concept of retreat and do nothing is a popular suggestion and, in the author’s opinion, is typically
presented by groups or individuals who do not have a personal stake in or ownership of coastal property
that is eroding. In other instances doing nothing is a hard decision driven by property owners’ financial
position. In the present situation this is a decision that would be made by the Provincial Parks Division,
typically in consultation with the local community and possibly at the behest of the community. The
author has no position on this option.
Conclusions and Recommendations
Port Hood Station Beach and Park is an interesting study area with respect to decade-scale changes in
coastal processes and how these processes can effect coastal erosion, or the lack of erosion as it may be.
The detailed studies by Taylor (2004) and Taylor (2005) have allowed the author to examine these
changes on a decadal time scale. During the period 2004 to 2014, the overall dominant process at the
Port Hood Station Beach has changed from one of erosion and instability to one of foredune stability,
growth, migration and even upper shoreface progradation (seaward advance). There are limited areas,
such as along the eastern end of the northwest-facing beach, where erosion is still problematic.
Figure 16. Sand trapping and vegetation growth between rocks placed along the seaward side of a dune, Cape
Breton Island.
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This change in coastal process is perhaps surprising. However, despite what is a general perception, both
within the scientific community and the general public, not all beaches in Nova Scotia are eroding. In
the author’s experience, new coastal areas (e.g. beaches) in Nova Scotia are continually being found that
are stable or even building seaward. The important take-away point of this study is that predicting future
changes of coastlines on multi-decadal scales is difficult, even by highly qualified and experienced
geoscientists and coastal engineers. In the author’s opinion this is true of most natural processes.
Local residents expressed concern about migration of the foredune that is burying a significant section of
the boardwalk, and erosion and wave action that are undercutting and causing failure of a section of the
boardwalk and observation platform. There is no solution to the present burial of the existing boardwalk
due to landward growth of the beach foredune. Scenarios for stabilization of the eastern portion of the
northwest-facing beach suggested by Taylor (2004) and Taylor (2005) were examined and discussed.
The only viable options in the author’s opinion are armouring or beach nourishment, but retreat and
abandonment should not be excluded.
The section of boardwalk and the observation platform, both of which were recently damaged, were
examined. It was concluded that the observation platform is not sustainable as a platform exposed to
wave impact and sea ice due to its original design and recent repairs. In the immediate future, the nuts on
the bolts inserted under the platform during the 2014 repairs should be tightened. Consideration should
be given to placing a second bolt through each of the supporting legs. The ends of the existing bolts
should be cut off once the nuts are tightened. At present they represent a safety hazard, particularly to
children who can easily crawl under the raised platform.
Armouring and beach nourishment were discussed in some detail in this report. Both options have
associated risks and potential benefits. A hybrid option involving aspects of beach nourishment and
armouring was described. The major factor in both of these options is cost. However, as discussed in the
report, due to very favorable construction conditions, cost associated with these options should be on the
low end of the scale. If interested parties wish to discuss these options further they should feel free to
contact the author.
If there are other questions or concerns with any aspect of the report, readers should direct enquiries to
the author at the Department of Natural Resources. Finally, Port Hood Station Beach has excellent
facilities, had heavy demand when the author visited the park in late July, and is a testament to the
efforts of the local community.
References
Reckendorf, F. 1998: Geologic hazards of development on sand dunes along the Oregon coast; in
Environmental, Groundwater and Engineering Geology: Applications from Oregon, ed. Scott Burns;
Star Publishing Company, Belmont, California, p. 429-438.
Taylor, R. B. 2004: Port Hood Coastal Foreland, Inverness County; Geological Survey of Canada
(Atlantic), unpublished report, 8 p. Copy available at the Nova Scotia Department of Natural Resources
Library.
Taylor, B. and Soehl, V. 2005: Port Hood Station Beach; Jacques Whitford, Dartmouth, N.S., 9 p. Copy
available at the Nova Scotia Department of Natural Resources Library.